Macrozamia glaucophylla

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Figure 1. M. glaucophylla leaf detail.

Contents

Introduction:

Macrozamia glaucophylla is a small to medium sized (Section Parazamia) cycad that is endemic to New South Wales. It has a subterranean caudex and normally has fronds with divided pinnae.

History:

M. glaucophylla was described and named by David Jones in 1998, when it was recognised as a separate and distinct species. It had previously been identified under the M. heteromera umbrella and was known as either Macrozamia sp. "Northern Pilliga" or as the "blue form" of M. heteromera. It was named after its glaucous blue leaves.

Distribution Range:

The distribution range of M. glaucophylla is restricted to the northern section of the Pilliga State Forest, south of Narrabri. The Pilliga State Forest, which occupies an area of some 380,000 hectares, between Coonabarabran and Narrabri, is locally known as the "Pilliga Scrub" (or simply "the Pilliga"). The Pilliga State Forest adjoins the 80,000 hectare Pilliga Nature Reserve, which was created in 1968. The total area of the Pilliga thus exceeds 450,000 hectares (including some privately owned land).

Habitat Conditions:

M. glaucophylla usually grows in a pattern of isolated individual plants; while in some scattered locations it forms small thickly populated stands. M. glaucophylla grows in deep sandy soil, under a sparse canopy of either Callitris spp. (principally Callitris glaucophylla - the "White Cypress Pine") or Eucalyptus spp. (principally Eucalpytus creba - the "Narrow-leaved Ironbark"). Acacia spp. are also common. The canopy cover provided for M. heteromera is the most open canopy cover for any cycad population in New South Wales.


Figure 2. M. glaucophylla with young female cones.

Climatic Data:

Narrabri (elevation 212 metres) has an annual average rainfall of 660 mm (spread over 64 rain days) with winter minimum and summer maximum daily temperatures, reached at least once per week in July and January, of -0.8°C and 37.6°C. respectively. Frosts occur on an average of 29 days per year.

Rainfall Patterns:

One-third of the annual rainfall at Narrabri falls sporadically during summer, with the balance of the rainfall being spread evenly (on a seasonal basis) over the rest of the year. The seasonal rainfall pattern is as follows: Summer: 33%, Autumn: 22%, Winter: 21% and Spring: 24%.

Principal Characteristics:

The principal characteristics of M. glaucophylla are as follows:

  • a normally unbranched subterranean caudex
  • pinnae which are normally, though not always, divided
  • pinnae that rise from the rachis to form a "V"-shaped profile
  • pinkish-red callouses at the point where the pinnae join the rachis, but these callouses undergo a colour transformation with age and change from pinkish-red to a creamy-white colour
  • fronds which are strongly recurved near the apex
  • fronds which reach an average above ground height of 50-70 cm, ranging up to a

maximum length of approximately 1.1 metres

  • new fronds that are a striking glaucous blue colour which, with age,

changes to a faded pastel blue-green colour

  • seeds with red coloured flesh.


Figure 3. M. glaucophylla with young male cones.

Plants:

The number of fronds on M. glaucophylla normally ranges up to about 10, but there is a marked difference in size and symmetry between plants that grow in the northern and southern sections of its habitat. M. glaucophylla is more robust in the northern part of its distribution range, with plants generally having longer and more numerous fronds than plants in the southern part of the distribution range.

Moreover, these robust plants usually have longer and broader pinnae than either M. heteromera or M. stenomera, with the sub-leaflets being prone to extending and overlapping each other in an inconsistent and untidy manner " which tends to give the fronds a "bushy" appearance.

In addition, plants in the far north of the distribution range, that grow close to the edges of normally dry creek beds, have longer and more numerous fronds than plants growing in other locations in the northern sections of the distribution range; and it is probable that plants which grow near some of these creek beds (with their ephemeral water flows) are those, as described by David Jones, with up to 25 fronds. The reason for this north-south variation in plant size is puzzling.

Fronds:

Emerging fronds of M. glaucophylla are somewhat like emerging fronds of L. peroffskyana insofar as they rise almost vertically, with furled pinnae, for a considerable portion of their ultimate length before the pinnae begin to unfurl (See Figure 10).

Pinnae:

M. glaucophylla generally has fronds with divided pinnae, with a normal division into two sub-leaflets. A second division is not uncommon and can result in either 3 or (very infrequently) 4 sub-leaflets being formed.

Figure 4. Female M. glaucophylla with a disintegrating cone.

Cones:

The female cones on M. glaucophylla are the largest of any Section Parazamia species in New South Wales. The coning cycle of this species is irregular. When coning does occur, however, a large percentage of both male and female plants in the thickly populated stands usually participate in the process. After such a coning episode, we saw numerous female plants with two cones; and numerous male plants with up to four cones.

Seeds:

Seeds from the above coning episode were plentiful on the ground near female plants, with the flesh having been removed by kangaroos. Possums are also involved in eating the flesh of the seeds, but they usually take the seed to a nearby tree and, after eating the flesh, drop the seed underneath the tree. Seeds were also sighted with what appeared to be numerous teeth marks, which we concluded were made by feral pigs.

Seeds of M. glaucophylla (from plants in the northern part of the distribution range) are larger than the seeds of M. diplomera and, also, M. heteromera and other Section Parazamia species. On a comparative basis, the seeds of M. diplomera are larger than the seeds of M. reducta plants which grow in the Newcastle/Cessnock area.

Comment:

Not withstanding the problems of plant identification and classification, the physical difficulty of locating plants within the Pilliga State Forest is complicated by having to drive on forest tracks that often degenerate into sand drifts (and which can only be traversed, with great difficulty, in a conventional drive vehicle) and, also, by the occasional sighting of feral pigs wandering around within the confines of the forest. The feral pigs add a new dimension to the hazards caused by kangaroos and emus which can suddenly dash across the road in front of you as you are driving along looking for cycads (which can sometimes be completely hidden in the undergrowth).


Figure 5. M. glaucophylla with "bushy" fronds.


Bushfires:

Large-scale bushfires occur periodically in the Pilliga. In 1951 a massive bushfire raged through 350,000 hectares. Huge bushfires (exceeding 100,000 hectares) have since occurred in 1982, 1997 and 2006. Paradoxically, following the 1997 fires, the Pilliga was subject to major flooding.

Affinities:

In respect of New South Wales cycads, prior to the 1998 revision of the M. heteromera complex by David Jones, there were only three named species with divided pinnae M. heteromera and M. stenomera (which are Section Parazamia cycads) and M. diplomera (which is a Section Macrozamia cycad).

Two new Section Parazamia cycads, with divided pinnae, were subsequently named by David Jones M. glaucophylla and M. polymorpha. M. glaucophylla normally has divided pinnae on most of its fronds, whereas M. polymorpha generally has fronds with entire pinnae, but fronds with a combination of divided and entire pinnae are not uncommon. On an affinity basis M. glaucophylla is related to both M. stenomera and M. heteromera.

Disregarding colour variations, M. glaucophylla plants growing in the northern parts of the distribution range are usually large plants, which (when compared with plants in the southern parts of the distribution range) have longer and more numerous fronds, with crowded pinnae that give the fronds a "bushy" appearance, similar to that of M. stenomera, though the multi-divided pinnae of M. stenomera simplify any identification problems. On the other hand, plants growing in the southern parts of the distribution range are much smaller and, in general appearance, are more akin to M. heteromera, with its smaller stature and shorter and more orderly pinnae. There is only a very distant relationship between M. glaucophylla and M. polymorpha.

Figure 6. M. glaucophylla - robust plant with two female cones and "bushy" fronds.
Figure 7. M. glaucophylla - small plant.
Figure 8. M. glaucophylla - small plant.
Figure 9. M. glaucophylla - bushy fronds.
Figure 10. M. glaucophylla - new fronds about to unfurl.
Figure 11. Habitat - dry creek bed.
Figure 12. Habitat after of a bushfire.


Contributed by:

Craig Thompson and Paul Kennedy (Text & Figures1-12)
Note: This article is part of a major revision of an article by Paul Kennedy about Macrozamia heteromera
that was published in Vol. 59 of Principes minor in November 1992, prior to the 1998 revision of the M. heteromera complex by David Jones.

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